In turbine stages, it is known to provide turbine moving blades with a shroud band. In this case, the shroud band coupling of the blades or blade segments lying next to one another is characterized by a defined coupling angle, which, however, is affected by centrifugal forces acting on the blades, by the blade untwisting, by the shroud band stretching, by the temperature of the working medium, etc. The stresses which act during the mutual support of the blades during operation can in turn be controlled by the coupling angle and the coupling area. Such turbine moving blades having a shroud band segment are described, for example, in German patent DE 36 20 162 C2, related to U.S. Pat. No. 4,699,569 and German Patent DE 35 17 283 C2, all of which are incorporated by reference herein.
The type of coupling, i.e. the coupling angle and the coupling area, is of considerable importance for the operating behavior of the turbine moving blades, and here in particular for the wear behavior in the region of the coupling, on account of the transmission of the coupling forces. On account of the abovementioned factors which affect the shroud band coupling, even small changes to the turbine design of individual turbine stages, for example by conversion of a turbine stage or through changed operating conditions, may lead to undesirably high wear on existing turbine stages. If it is found on the basis of operating experience that the wear in the coupling region of two turbine shroud band segments is inadmissibly high, the procedure hitherto has simply been to repair the turbine blade in the coupling region. In the process, the coupling region is as a rule coated with chromium carbide. In the extreme case, individual blades or blade groups have to be exchanged. In addition, the maintenance intervals are shortened in the most unfavorable cases, which reduces the efficiency of the plant.